Field of the Invention
This invention relates to medicinal dressings that provide an advanced healing environment for wounds. Good wound healing is characterized by rapid and complete regeneration of the damaged tissue. Considerable efforts have been expended in the study of wound dressings with the aims of finding which dressings are most effective in promoting wound healing. The process of wound healing is complex and is not fully understood. High macrophage activity is desirable, particularly during the early stages of healing, to kill bacteria and to remove cell debris and foreign matter. This activity is generally accompanied by inflammation. High fibroblast activity is desirable, particularly during the later stages of healing, to produce a high rate of regeneration.
Enhanced concentrations of active free radicals are often found in wounds, in particular small oxygen-containing free radicals such as the hydroxyl radical (OH.), the hydroperoxyl radical (OOH.) and the superoxide anion (O.sub.2.sup.-). The latter two are in protonation equilibrium, with the anion predominating at physiological pH; the hydroperoxyl radical is a more active free radical than the superoxide anion. The presence of these radicals is believed to be advantageous in the early stages of healing, attracting macrophages into the wound and promoting the respiratory burst. Their continued presence is, however, believed to be detrimental. They are thought to promote continued inflammation and so to delay healing and in severe cases to induce tissue necrosis and permanent tissue damage. In contrast, oxidizing species without unpaired electrons, such as hydrogen peroxide (H.sub.2 O.sub.2), are believed to be considerably less harmful.